WASHINGTON (AP) -- The Senate pushed toward a historic vote on legislation outlawing workplace discrimination against gay, bisexual and transgender Americans, demonstrating the nation's quickly evolving attitude toward gay rights nearly two decades after Congress rejected same-sex marriage.
All 55 members of the Democratic majority, including senators from the Deep South, and several Republicans were expected to unite on Thursday in backing the Employment Non-Discrimination Act. Sen. John McCain, the GOP's presidential nominee in 2008, signaled his conditional support on Wednesday.
"It is time for Congress to pass a federal law that ensures all our citizens - regardless of where they live - can go to work unafraid to be who they are," said Senate Majority Leader Harry Reid, D-Nev., who urged House Speaker John Boehner, R-Ohio, to reconsider his opposition.
The enthusiasm of the bill's supporters was tempered by the reality that the Republican-led House, where conservatives have a firm grip on the agenda, is unlikely to even vote on the legislation. Boehner maintains his longstanding opposition to the measure, arguing that it is unnecessary and certain to create costly, frivolous lawsuits for businesses. Outside conservative groups have cast the bill as anti-family.
In the Senate, opponents of the legislation remained mute through three days of debate, with no lawmaker speaking out. That changed on Thursday as Republican Sen. Dan Coats of Indiana said the legislation would force employers to violate their religious beliefs, a direct counter to rights embodied in the Constitution.
"There's two types of discrimination here we're dealing with, and one of those goes to the very fundamental right granted to every American through our Constitution, a cherished value of freedom of expression and religion," Coats said.
The Senate rejected an amendment sponsored by Republican Sen. Pat Toomey of Pennsylvania that would have expanded the number of groups that are covered under the religious exemption. Opponents argued that it would undermine the core bill.
Senate passage would be a major victory for gay rights advocates in a momentous year for the issue. The Supreme Court in June affirmed gay marriage and granted federal benefits to legally married same-sex couples. In the heartland, Illinois is on the verge of becoming the 15th state to legalize gay marriage, along with the District of Columbia.
"I hope that we are on the verge of making history tomorrow by passing this bill with a strong vote," Sen. Susan Collins, R-Maine, said Wednesday. "I then hope that our colleagues on the House side will follow suit and that we can see this bill signed into law."
If the House fails to act on the bill, gay rights advocates are likely to press President Barack Obama to act unilaterally and issue an executive order barring anti-gay workplace discrimination by federal contractors.
Through three days of Senate debate, backers of the bill repeatedly described it as an issue of fairness some 50 years after Congress passed and President Lyndon Johnson signed the Civil Rights Act.
"It is well past time that we, as elected representatives, ensure that our laws protect against discrimination in the workplace for all individuals, that we ensure ... some protections for those within the LGBT community," said Sen. Lisa Murkowski, R-Alaska, who described the diversity in her state.
Murkowski's support underscored the generational shift. Seventeen years ago, when a bill dealing with discrimination based on sexual orientation failed by one vote in the Senate, the senator's father, Frank, voted against it. That was the same year that Congress passed and President Bill Clinton signed the Defense of Marriage Act.
Current federal law prohibits discrimination on the basis of sex, race and national origin. But it doesn't stop an employer from firing or refusing to hire workers because they are gay, lesbian, bisexual or transgender.
The bill would bar employers with 15 or more workers from using a person's sexual orientation or gender identity as the basis for making employment decisions, including hiring, firing, compensation or promotion. It would exempt religious institutions and the military.
By voice vote Wednesday, the Senate approved an amendment from Republican Sens. Rob Portman of Ohio and Kelly Ayotte of New Hampshire that would prevent federal, state and local governments from retaliating against religious groups that are exempt from the law.
The Senate planned to vote Thursday on an amendment by Sen. Pat Toomey, R-Pa., to expand the number of groups that are covered under the religious exemption.
Likely Senate approval of the overall bill reflects the nation's growing tolerance of gays and the GOP's political calculation as it looks for supporters beyond its core base of older voters. A Pew Research survey in June found that more Americans said homosexuality should be accepted rather than discouraged by society by a margin of 60 percent to 31 percent. Opinions were more evenly divided 10 years ago.